congesting a back-to-back link on a switch

Jul 07, 2007 1 Replies

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Hello experts,

Traffic source1 -------- Catalyst1 --------------Catalyst2

---------Traffic source 2

----------------------------------------Direction of Traffic flow ----------------------->>>

Is there any way to congest the RX link on catalyst2 in above setup. Basically I am trying to force the generation of flow control frames between catalyst2 and catalyst1. Idea is if catalyst2 gets congested on RX side, it will trigger flowcontrol frames to catalyst1 and then catalyst1 should react to it.

I think the only way to congest will be to decrease the RX buffer size on catalyst2. Does anybody know how to achieve that on a RX port which has following capablity....

GigabitEthernet1/1 Dot1x: yes Model: WS-X6748-SFP Type: 1000BaseT Speed: 1000 Duplex: full Trunk encap. type: 802.1Q,ISL Trunk mode: on,off,desirable,nonegotiate Channel: yes Broadcast suppression: percentage(0-100) Flowcontrol: rx-(off,on,desired),tx-(off,on,desired) Membership: static Fast Start: yes QOS scheduling: rx-(1q8t), tx-(1p3q8t) CoS rewrite: yes ToS rewrite: yes Inline power: no SPAN: source/destination UDLD yes Link Debounce: yes Link Debounce Time: no Ports on ASIC: "bunch of ports" Port-Security: yes

Any advide will be helpful. Thanks, Akmann

The 6724 card has 20 Gbps full duplex backplane link, and is split into 2 12 port sections fed by separate chips.

and if there is a DFC on this blade, then L3 forwarding happens locally, so the backplane doesnt get touched for local traffic.

reducing the buffer pool would only help if there was more traffic coming in that could get out again. Otherwise there is very little in the buffers since packets go straight thru to the backplane.

basically if you want congestion you are going to have to load that and lots of other ports with wire speed traffic - preferably using small packets to increase the overhead in the backplane.

you need to congest somewhere else unless you have a 15 to 20 port GigE traffic generator.....

congesting a back-to-back link on a switch

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